Neumann W492 equalizer DIY project (PCB docs added)

[cannikin]

Anyone want to buy some OPA2604AP with me to replace the 5532?

Newark gives a 40 cent price break over 25? so with 2 stereo channels thats 32 which means $5 off the price without shipping.

 

[RedNoise]

Hi Cannikin! 2604 or 2134 ????I'm in , dependin on price !
Email me if you want !

 

[jarlehal]

Hi folks. I need a little help troubleshooting my W492s. I built two of them and all tested well at first. But now I can't figure out what is wrong.

I'm using a SSL9K PSU board fitted with 7815/7915 (left out components of the 48v rail). PowerTX is a 50VA,2x15V toroid. I've used this board for my Fetboys and my 312s which all work great.

Well, strange thing on this unit is that sometimes my 7815 output voltage is 0.8V. Seems totally random, sometimes when I power up the EQs I get the correct voltages and all is fine, the next time it's dead. Then when 0.8V at the output of the reg, there's still fine voltages both the negative rail and before regulation on the positive rail.. I've never seen the 0.8V output without load though..

I've tried swapping out the 7815 - no luck.
Changed the ceramic (100n) on the +15V output rail - no luck.
I've tried powering only one of the EQ boards - same thing, both channels...

Clue anyone?

EDIT:
The unit was in the "dead state" just now, and I accidentally shorted the input of the 7815 to ground with my probe - and suddenly the unit came alive  What's going on? Next power up - WORKS - then WORKS again - then DEAD...  aaarghhh 


J

 

[cannikin]

Can't really help you but I have a power related intermittency issue on one channel.  which is really strange.  the EQ will go on-off-on-off

 

[mitsos]

I can't say if this is happening with you guys, but I recently had this problem with a pair of home-etched 312s running on a working Fabio PSU. Everything was working fine for about a week, and the day I take it over to a buddy's studio to show him, it craps out! Talk about embarrassing, at least the singer he was recording that day had already left.  I don't remember the details but I somehow had two ground references (case and power) and ended up with 0V on phantom and the thing didn't work. When I put all the 0V references together it came to life! Probably not related to your issues, but throwing it out there anyway.  Is AudioX around to shine a light maybe?

Cannikin, what PSU are you using out of curiosity?  Did you build with 2604 or 5532?  If still interested try seller AudioTek168 on ebay. They sell them for 6.99 a pair with free shipping from Taiwan. If ordering that many, they'll probably cut you a better deal.

Have you guys gotten to testing them (soundwise) at all? I am ordering my pots from TAW this week and I think I have everything else, so looking forward to getting these done!

Good luck with getting it solved!  Keep us posted!

 

[jarlehal]

Mine has 5532, and it's my first EQ project. Not calibrated - and no "soundwise" test yet..

Well, what I think I'll do next is to redo my AC IN->Toroid->PSU wiring. I've read some posts about the isolation on toroid leads causing some trouble. Could it still be faulty wiring, even if my voltage readings are correct (before regulation)? What will happen if one of the leads I use as CT isn't connected ,or has a bad connection, to GROUND??

 

[mitsos]

What will happen if one of the leads I use as CT isn't connected ,or has a bad connection, to GROUND??

It sounds like you have a suspicion? I am no expert, but it makes sense that if you disconnect the 0V of one secondary that part of the circuit has no 0 reference. Kind of like the problem I had except mine was after regulation. Either way though, that part of the circuit had no 0V and I read 0V on phantom. So, yeah, I'd check that for sure... Let us know what you find.

 

[rhodes54]

Hi all,

I'm about to start building the 492W EQ and need to order the pots. I have a question about the OMEG pots:
- Do they work ok as they are lot cheaper than vishays.
- Do the OMEGs fit in the PCB or do they need to be wired?

Thanks!

 

[Harpo]

The unit was in the "dead state" just now, and I accidentally shorted the input of the 7815 to ground with my probe - and suddenly the unit came alive  What's going on? Next power up - WORKS - then WORKS again - then DEAD...  aaarghhh 

What specific voltage regulators do you use ? Never had trouble with LM78xx/uA78xx/LM79xx/uA79xx, but some, like TS7815 / TS7915, seem to be famous for hanging at power up.

 

[mitsos]

I have a question about the OMEG pots:
- Do they work ok as they are lot cheaper than vishays.
- Do the OMEGs fit in the PCB or do they need to be wired?

It's funny since I put the order together, but I haven't gotten mine yet. Need to get my act together and place my order. The pots should "work" just fine. They are conductive plastic just like the vishays, which is a requirement for this circuit.

About fit, the single gang ones should fit perfectly, as they have the same lead spacing. The dual gang, on the other hand, will require a slight bending of the leads. The spacing between gangs on the Omeg IIRC is 7.5mm and the Vishays are 5mm. The difference is 2.5mm, so 1.25mm bend inwards in each set of legs should do it. Shouldn't have a problem, just don't go crazy with the bending.

 

[jarlehal]

I use LM7815/LM7915.. Tried to swap the reg of the positive rail, but that didn't change things..
My second son was born a week ago, so I haven't been able to look at this much.
But now I had a little time to redo the connections between the toroid and the PSU board. Cut the secondary leads and scraped off all the insulation, but sadly that didn't help either. At first I thought I'd fixed it as the unit work on about 10 power ups in a row, but no. Still dead at random power ups.

EDIT: Also did the AC in -> toroid connection again - no luck.. Aarrghh

 

[chrissugar]

I read the first page of this thread, and became interested to build one channel of this EQ just to test it if it's suitable for my needs, just to discover later that there are no PDFs for self etching.
OK, I can understand that based on some previous negative experiencees people are not happy to post their PCB files, but this is an old, not anymore manufactured product for more than 20 years. And the most hilarious thing is that a complete original W492 on ebay is around 250euros which is just a little bit more than the price of the components for the DIY version. Maybe I'm a bit stupid but I can't understand how someone would build this thing and make profit by selling a clone on ebay. Or maybe it is a bit to much paranoia.

The sad thing is that this place is becoming more and more like the forums (forums I don't like) where you can try a project only if you buy the boards. This is so sad.
Most of the people from this group developed their skils by building/trying some of the projects available for free from some of the generous people, and now many of them are advocating for not publishing this info for free.

Anyway, I'm not afected by this because I design/redesign all the PCBs for all of my  projects, but sometimes it is great to have some PDF for self etching just to try if a projects suits your needs.

Sorry for this post but I'm so disapointed by this state of things.

chrissugar

 

[jarlehal]

Chris:
Have you tried contacting audiox? Based on the discussion prior to the PCB production, I think audiox might be able to help you out.
Personally I just love the PCB services provided here, and I don't really understand your frustration. The PCBs are fairly priced, and if the build doesn't suit your needs, then sell it over at the black market.

As for my unit, I gave up  Changed the PSU to a Mnats I had laying around. And now I think it's finally cured !!!
Pictures coming up shortly..

 

[mitsos]

Sorry for this post but I'm so disapointed by this state of things.
chrissugar

I would also say to contact Audiox. Once you add up the costs with the vishay pots, it doesn't make much sense at all. I too would have liked self etch boards (they are double sided though, a bit more of a PITA)....

Anyway, if you decide to do this, call Laura at TAW for some Omeg ECO cond plastic pots for this.. She ordered them for this project, they should work fine and cost about $18 a channel...

 

[jarlehal]

Here's my finished unit.
Thanks to AudioX & Gustav

 

[mitsos]

nice! how's she sound?  Did you do that front panel yourself? Would you mind sharing the graphics?

 

[jarlehal]

nice! how's she sound?  Did you do that front panel yourself? Would you mind sharing the graphics?

Haven't given her a too much of a "sound test" yet, but seems pretty nice so far.
Yes, the graphics are made with InkScape and stored in SVG. I have them on a memory stick that I can't find right now, but I'll upload the graphics when I do.

 

[mitsos]

Cool, appreciate it. One less step to keep me from finishing.. If it sound as good as it looks, it'll be amazing!

 

[inputoutput]

KNALL!!!!  (great work)

 

[RedNoise]

Jarlehal : Nice Job!!!!!